Details on this are slim, even in Memory Alpha. Was Pon Farr always based on a seven year cycle? Or is this the result of Vulcans attempting to control the urges and to subjugate their urges to the logic and philosophies of Surak?
As you say, details are sketchy. Vulcans rarely speak of it, to outsiders or to each other. But it does appear to be a biological trait of the Vulcan species, and always has been. There is no information available to the contrary.
The ritual of koon-ut-kal-if-fee, adopted after the Time of Awakening, seems to be an attempt at logically structuring or controlling the pon farr impulses, in-line with Surak's teachings.
It is reasonable to assume that the reason for the mystery and secrecy surrounding pon farr have to do with post-Surak Vulcans' embarrassment over the loss of their logic. From Amok Time:
KIRK: [...] Well, there's no need to be embarrassed about it, Mister Spock. It happens to the birds and the bees.
SPOCK: The birds and the bees are not Vulcans, Captain. If they were, if any creature as proudly logical as us were to have their logic ripped from them as this time does to us. How do Vulcans choose their mates? Haven't you wondered?
KIRK: I guess the rest of us assume that it's done quite logically.
SPOCK: No. No. It is not. We shield it with ritual and customs shrouded in antiquity. You humans have no conception. It strips our minds from us. It brings a madness which rips away our veneer of civilisation. It is the pon farr. The time of mating. [...]
In the TOS episode "The Cloud Minders", Droxine hits on Spock, and he responds somewhat coyly. Droxine puts this very question:
... is there nothing that can disturb that [seven year] cycle, Mr. Spock?
To which Spock replies:
extreme feminine beauty... is always disturbing.